The aim of this investigation is to determine the effect of free and forced convection on the distribution of heat in a fluid.
Azam Mir 31.10.2000 Heat transfer by convection Aim The aim of this investigation is to determine the effect of free and forced convection on the distribution of heat in a fluid. Introduction Heat transfer by convection in this investigation occurs as a result of heat transferred from a solid surface to a fluid by conduction and then that heat is transferred within the fluid by the movement of exited particles. 'It is important to note that convection requires mixings of fluid elements, and is not governed by temperature differences.' (CRCE/Vol.1/ 2000Edt. pg381). Forced convection is generated using a magnetic stirrer and follower, which produce circulating currents within the water. The currents are formed by water from lower depth, when warmed, expand and rise due to its lower density than its surrounding environment; the empty space is replaced by colder water of higher density. Attention may be given specifically to the force convection, since we know that when the magnetic follower rotates, it increase's the velocity within the water, which would evenly spread the heat resulting in a more regular distribution of temperature throughout the beaker of water. Heat balances were calculated as they indicate the theoretical amount of heat (Qw) required to raise the temperature of the water in the beaker to its final temperature, this would be subtracted from the
The Heating Effect of An Electrical Current
SC 420 Principles of Physics Lab # 11 The Heating Effect of an Electric Current Group Members: Date Performed: April 25, 2007 Table 3. Verification of the principle of conservation of energy Work done by electric current Heat produced by electric current % W, J Q, J difference Run I 6200 J 5134 J 6.81% Computations Equation (3): W= I²Rt W = (2A)²(4.5?)(900s) = 16200J Equation (12): Q = (mwcw + mccc + mhch) (Tf-Ti) Q = {(.1672)(4186) + (.0474)(910) + (.015)(910)} X 20ºC = 15134J % difference: Table 4. Electromechanical equivalent of heat Work done by electric current, W,J Heat produced by electric current J = W/Q, J/cal % difference Run I 6200 J 3615 cal 4.48 J/cal 7% Computations Equation (9): Q = mwcw(Tf-Ti) + mcalccal(Tf-Ti) + mhch(Tf-Ti) 20{(167.2(1) + 47.4(.217) + 15(.217) =3615 cal Equation (13): J = W/Q % difference: Table 5. Dependence of the temperature on time Initial temperature, Ti = 21.9ºC Final temperature, Tf = 41.9ºC Voltage = 9.4V Amperage = 2A Time Time Run 1 min s I = 2A Temperature Temperature T, °C (T - Ti), °C 0 0 21.9 0.0 60 23.0 .1 2 20 24.9 3.0 3 80 26.4 4.5 4 240 27.9 6.0 5 300 29.2 7.3 6 360 30.6 8.7 7 420 31.9 0.0 8 480 33.3 1.4 9 540 34.5 2.6 0 600 35.8 3.9 1 660 37.0 5.1 2 720 38.3
Amadeo Avogadro.
Amadeo Avogadro Amadeo Avogadro was an Italian scientist noted to be one of the founders of physical chemistry. He was actually a physics professor but he experimented in both physics and chemistry using mathematics to base most of his findings. Avogadro is well known for his hypothesis known as Avogadro's Law. His law states that a given temperature, equal volumes of gases contain the same number of molecules equal to 6.02252.1023. Avogadro received no recognition for his hypothesis or his constant during his lifetime because he was not considered as a brillant emperimenter but rather, a careless one. He also did not back up his hypothesis with an impressive display of experimantal results. He also did not have an impressive reputation for accurate experimental work. Another reason why his hypothesis was not recognized was because of the fact that his work was published in obscure jounals and maybe because he was very isolated from the mainstream of chemistry done in his time. Avogadro's work was recognized nearly fifty years after he had made his hypothesis. Two years after his death, his colleague showed how the use of Avogadro's number could solve many of the problems in chemistry. This time Avogadro's paper was looked at more carefully over a wider and more distinguished group of scientists, thus his work was finally recognized. Avogadro's work helped other
Ionisation energy as evidence for sub-shells
Ionisation energy Ionisation energy as evidence for sub-shells Ionisation energy is a measure of the ease in which atoms lose electrons and become positive ions. The first ionisation energy is the energy required to remove one electron from each atom of a mole of gaseous atoms. M(g) - e- M+(g) Further electrons may be removed giving successive I.E. M+(g) - e- M2+(g) This energy is usually quoted in units of kilojoules per mole (kJ mol-1). Energy is required to remove an electron from any atom because there is an attractive force between the nucleus and the electron being removed which has to be overcome. The value of the first ionisation energy depends upon: ) The effective nuclear charge 2) The distance between the electron and the nucleus 3) The 'shielding' produced by lower energy levels Shielding involves the repulsion between electrons in inner, filled orbitals and electron being removed from the outer orbital. The graphs of atomic number against first ionisation number show that across each period there is an increase in ionisation energy. Beryllium (Group II) has an extra electron and proton compared with lithium. The extra electron goes into the same 2s orbital. The increase in ionisation energy (I.E.) can be attributed to the increased nuclear charge. The ionisation energy of Boron is less than that of Beryllium because in Boron there is a
What are free radicals?
What are free radicals? Why are they damaging to the human body? And how does vitamin E and the other antioxidant nutrients help protect the body against free radical damage? We'll attempt to answer these questions and help you understand why eating 5-8 servings per day of anti-oxidant rich fruits and vegetables can benefit your health. But first, a little background... Background: A Brief Look at Chemical Bonding To understand the way that free radicals and antioxidants interact, you must first understand a bit about cells and molecules. So here's a (very) brief refresher course in Physiology/Chemistry 101: The human body is composed of many different types of cells. Cells are composed of many different types of molecules. Molecules consist of one or more atoms of one or more elements joined by chemical bonds. As you probably remember from your old high school days, atoms consist of a nucleus, neutrons, protons and electrons. The number of protons (positively charged particles) in the atom's nucleus determines the number of electrons (negatively charged particles) surrounding the atom. Electrons are involved in chemical reactions and are the substance that bonds atoms together to form molecules. Electrons surround, or "orbit" an atom in one or more shells. The innermost shell is full when it has two electrons. When the first shell is full, electrons begin to fill the
Describe the experiment, which led to the modern-day theory of the structure of the atom.
Chemistry Assignment #1 Describe the experiment, which led to the modern-day theory of the structure of the atom. An atom is the smallest particle that an element can be broken down into, which still retains all the properties, of the element itself. All substances are made from matter and all matter is made up of atoms. Today, in science, it is believed that atoms contain three inner particles: electrons, protons and neutrons. Protons are thought to possess positive charges and are located in the nucleus of the atom, along with neutrally charged neutrons. This nucleus is thought to be at the centre of the atom and is also thought to be responsible for 99.97% of the mass of the atom. Electrons are thought to be negatively charged species, which orbit the nucleus in shells. Figure #1 shows the model of the atom accepted today. This modern-day theory of the structure of the atom is a result of the works of many past scientists, both chemists and physicists. These include John Dalton, Joseph J. Thomson, E. Goldstein, Ernest Rutherford, James Chadwick and Niels Bohr. First in 1808, John Dalton came up with the Atomic Theory. He believed that atoms were the smallest particle of matter that could take place in a reaction. He also believed that they were indivisible and could not be created or destroyed. Then in 1897, J. J. Thomson discovered the electron. He found them to be
Measurement of gravity using a rigid pendulum
Measurement of Gravity Using a Rigid Pendulum Abstract In Bristol the acceleration due to gravity was measured using the Rigid Pendulum method. This involved timing small oscillations of a compound pendulum, and taking moments of inertia about the axis of rotation of the pendulum. Precise evaluation of the measurements taken shows the value for gravity, g, in this locality to be 9.89 ± 0.038 ms-2. This result is slightly higher than the values for g calculated previously, this inconsistency and its causes are examined. Introduction Of all the forces that act on us each day, gravity is the one force that we are all aware of. Newton was the first to underline the principles of gravity; each particle with a mass attracts all other particles with mass, with a gravitational force that is directly proportional to the product of their masses and inversely proportional to their distance of separation squared. This leads to show that on Earth a mass will have an acceleration due to the gravitational force of the earth, g, because from Newton's second law force is proportional to acceleration [1]. This value g is of course dependant on the distance to the centre of the Earth and there therefore will be minor differences in its precise value in different areas of the world. Due to these fluctuations in the Earth's gravity, the local value for g is very useful for various
The Geltard Classification
The Geltard Classification Geltard suggested a four-group classification within which the range bed behaviour under ambient conditions can be categorized on the basis of the particle and fluid density difference and the average particle diameter. Gelatrd's categories are referred to as groups, A, B, C and D. Group A powders are typically made up of materials with a small mean size and low particle density (less than 1.4 gcm-3). Beds of powders in this group undergo considerable expansion before bubbling commences. Also, when the supply of gas is abruptly cut off, the bed collapses slowly, typically at rate of 0.3 to 0.6 cms-1, this being similar to the superficial velocity of the gas in the dense phase. The circulation of the solids, on a large scale is visible when such powders are fluidised. Also, the bubbles in these beds appear to have a maximum size. This suggests the bed expansion and mean density would vary in linear fashion with fluidising gas velocity. The maximum stable diameter of the bubbles appears as a consequence of the shearing force created due to the downward movement of solids relative to the bubble. This force creates a circulation within the bubbles, the velocity of which attains the rise velocity of bubbles. When these bubbles coalesce the solids in the wake are pulled up, tearing the bubble, and the mechanism restricts the maximum stable size. FCC
What is a quantum computer?
Quantum computers have been a theory that has just been evaluated recently. It is to develop a computer that is faster than a giga hertz. What is a quantum computer? A normal computer codes information using a binary code. A bit can therefore be found either in the form of 0 or 1.We can picture a bit as an electron where the spin of an electron can be up which can be represented as a 0 and the spin of an electron down is 1. If we look at quantum mechanics, than we can deduce from the law of superposition that both states could occur simultaneously. This means a electron can spin up and down at the same time. Therefore if one qubit has two states then two qubits could be in four possible states i.e. 00, 01, 10 and 11. This means that you can do four numbers can be stored at once. So if there were 3 qubits then 8 different numbers can be stored simultaneously1. So we can see that there is an exponential increase so if n qubits were used to make a computer then 2n calculations can be done at once. Physicists are excited by the prospect because this means that unsolved problems and calculation could be solved by a quantum computer and the possibility of simulations being created that look very real. Problems faced making a quantum computer? One of the problems is how to get the qubits in two states simultaneously because the quantum states of a qubit can easily be disturbed
The atomic bomb is often found to be very controversial and complex by many people.
The atomic bomb is often found to be very controversial and complex by many people. Many people wonder why it was developed in the first place and why we used it against Japan. These answers are quite simple and will be answered in the following text. Two things people often overlook when thinking about the atomic bomb are its history and what it did for modern warfare. Many people do not know that the atomic bomb's history and its effects have changed the history of war forever. The principles of the atomic bomb are quite simple, contrary to popular belief. Many people think that some how an atom is split which causes the explosion. The splitting of the atom is true but its principles and construction go much deeper. The process of splitting atoms is known as nuclear fission. The best type and most commonly used atom to perform nuclear fission is the uranium-235 atom. Nuclear fission is performed by a scientist taking an atom and using a chemical reaction to fire a neutron at the uranium-235 atom. Once struck by the neutron it splits into three neutrons and two nuclei and large amounts of radioactivity is released along with enormous amounts of energy. The other neutrons that were created from the original splitting of the uranium-235 atom can then hit other uranium-235 atoms causing them to split. This is known as a chain reaction. This reaction is very powerful and